The present invention relates to forms for relatively thin thickness concrete structures such as sidewalks, driveways, curbing, slabs and the like.
Forms for retaining wet concrete as part of the process of molding a relatively thin concrete flat work structure such as a sidewalk, driveway or slab, are quite often fabricated out of dimension lumber, such as a conventional two-by-four or a two-by-six. One or more two-by-fours, for example, are secured end to end on grade to become the form that defines one side edge of the concrete structure to be poured. Wooden or metal retaining stakes are driven into the ground adjacent the exterior side of each two-by-four to secure it in position against the pressure of the concrete poured between forms laid on each side of the structure to be poured. After the concrete has cured, traditional practice dictates that the retaining stakes and the two-by-fours be removed from the sides of the concrete structure. Following extraction of the stakes and forms, soil or other material is back-filled against the sides of the structure to produce an overall level surface with the top of the poured structure.
Several problems arise from this conventional method of erecting and stripping forms for a concrete flat work structure. First, wooden forms, described, must be removed after the concrete has cured, requiring manpower, time and expense. Secondly, after some use, the wooden form boards warp and bend, contributing to poor concrete edges and making the setting of the forms more difficult and time consuming. Sizing wooden forms to a particular job requires that the forming boards be cut to length, reducing their usefulness in future forming operations, thus wasting material.
Accordingly, the primary objective of the present invention is to provide a form for relatively thin, flat concrete work such as sidewalks, driveways and the like that eliminates the problems inherent in the use of the traditional wooden forming boards. This objective is affected by providing an expendable paper form that does not need to be removed from the structure following curing of the concrete. The corrugated paper form is left in place and soil or other back-fill material is deposited over the paper form which, after a period of time, disintegrates and is otherwise unobtrusive.
A second objective of the invention is to provide a disposable concrete form that can be transported in a flat, space-saving conformation and assembled for use at the job site.
The present invention provides an expendable corrugated paper form for concrete work that does not require stripping or removal following curing of the concrete. Instead of removing the paper form, it is left in place and soil or other back-fill material is deposited over it. The paper form disintegrates after a period of time.
To maximize shipping efficiency, the corrugated paper form is preferably assembled at the construction site from a flat blank. The blank has previously been prepared with scored folding lines and retaining stake apertures have been cut into the blank. When assembled, the folded and taped blank produces a sturdy box having a triangular cross-section and having vertically aligned apertures in the two sides of the box that define the base and hypotenuse of the triangular shape. Preferably, the box""s triangular shape is that of a right triangle where the base side is laid against the surface grade and the height side is disposed vertically to serve as the form against which the wet concrete is poured to create the desired structure. The aligned apertures in the hypotenuse and base of the box are positioned to receive one or more spaced apart stakes that protrude through the base and are driven into the ground on which the box form lies. In each of such forms, there are a plurality of apertures along its length to receive retaining stakes at intervals that are appropriate. The stakes secure the form box in its desired position and support it against the lateral pressure of the concrete against the height side. The box can be of any convenient length but preferably the blanks that form the box are made in standard six or eight foot lengths to produce a convenient working length for each form box.